One of the most useful permanent magnet structures is the hollow cylindrical flux source, or magic ring, which is a cylindrical permanent magnet shell that offers an interior magnetization vector that is more or less constant in magnitude throughout the interior cavity of the structure and produces a magnetic field greater than the remanence of the magnetic material from which it is made. The magic ring, also know as a magic cylinder or Halbach cylinder, produces comparatively high transverse fields in a cylindrical cavity which it encloses in the form of a cylindrical shell. They are well known and discussed in numerous publications and papers such as Rare Earth Iron Permanent Magnets, edited by J M D Coey, Oxford Science Publications (1996) and U.S. Pat. Nos. 5,382,936 and 5,428,335, both entitled “Field Augmented Permanent Magnet Structures,” in which this inventor was a co-inventor. FIG. 1 is a cross-sectional view of an abbreviated prior art magic ring magnetic structure, with 8 wedge-shaped pieces, the small arrows indicating magnetization direction of each wedge-shaped piece and the large central arrow indicating the magnetic field direction. FIG. 1 also illustrates the angles θ and γ. The magic ring can be also approximated by assembling transversely magnetized rods that are circularly arranged about a central cylindrical space.
If a transverse section of a magic cylinder is rotated about its polar axis its locus forms a magic sphere. FIG. 2 is a cross-sectional view of a prior art magic sphere magnetic structure with the small arrows indicating magnetization direction of each one of the numerous pieces assembled to form the prior art structure.
While the prior art magic ring and magic sphere structures each have a number of useful features and applications, they all suffer from one chronic disadvantage. The disadvantage with these magnetic structures is that they all require the painstaking assembly of numerous pieces with different magnetic orientations. For example, the magic sphere disclosed in Leupold U.S. Pat. No. 5,382,936 “Field Augmented Permanent Magnet Structures,” typically requires the assembly of at least 64 pieces with numerous magnetic orientations. Similarly, the magic ring typically requires assembly of as many as 26 different pieces with differing magnetic orientations. Such detailed fabrication and assembly requirements quickly lead to high manufacturing and assembly costs, as well as significant amounts of scrap material. For these reasons, there has been a need to assemble magic ring or magic sphere magnetic structures in a way that requires fewer piece parts, less assembly time and decreased manufacturing costs. Up until now, this need has not been answered.